Control arrangement in a pump having a pump chamber of periodically variable volume



NOV. 29, 1960 A SENMNG ETAL 2,961,965

CONTROL ARRANGEMENT IN A PUMP HAVING A PUMP CHAMBER OF PERIODICALLYVARIABLE VOLUME Filed Oct. 4, 1955 2 Sheets-Sheetl g1 INVENTOR5 BY fizzM 71/ ATTO EYS Nov; 29, 1960 AKE SENNING ETAL CONTROL ARRANGEMENT IN APUMP HAVING A PUMP CHAMBER OF PERIODICALLY VARIABLE VOLUME Filed Oct. 4,1955 2 Sheets-Sheet 2 United States Patent CONTROL ARRANGEIVIENT IN APUMP HAVING A PUMP CHAMBER OF PERIODICALLY VARI- ABLE VOLUIVIE AlteSenning and Per Anton Astradsson, Stockholm, Sweden, assignors toSvenska Aktiebolaget Gasaccumulator, Lidingo, Sweden, a corporation ofSweden Filed Oct. 4, 1955, Ser. No. 538,478

Claims priority, application Sweden Oct. 6, 1954 6 Claims. (Cl. 103-37)The present invention refers to an arrangement in a pump which has apump chamber of periodically variable volume serving for the control ofthe pump output by means of a pressure medium. The arrangement makespossible a continuous and easily adjustable regulation of the pumpoutput, for instance in response to the level of a liquid in a containerconnected to the pump intake.

The arrangement is characterized in that a pressure chamber with aresilient wall responsive to the pressure of the pressure medium isadapted to operate on the wall of the pump chamber in such a way thatthe magnitude of the periodic volume variation of the pump chamher andthus of the pump output increases with an increase in the pressure ofthe pressure medium.

The control arrangement according to the present invention isparticularly suitable for use in connection with a pump adapted forpumping blood, i.e. in a pump which is able to serve as an artificialheart. The invention will be further described with reference to thedrawings, in which: Figure 1 is a schematic drawing of an arrangementaccording to the present invention, and Figure 2 shows anotherembodiment of an arrangement according to the present invention.

The pump shown in the drawing is provided with two pump chambers 1 and 2connected in parallel and further connected via inlet valves 3 and 4 andoutlet valves 5 and 6 to an intake conduit 7 and an outlet conduit 8,respectively, for the liquid. In the present instance, the liquid isassumed to be blood, which is to be supplied to a patient after atreatment such as an oxygenation or the like. Each of the pump chambersis constructed with a wall of resilient material, which is exposed toperiodic pressure from without in order to vary the pump chamber volume.In the embodiment shown, the pump chambers are constructed of rubber,plastic or a similar soft material, and a wall of each pump chamber isacted upon by a crosspiece 10 attached to one end of a rod 9. The otherend of the rod is connected with an eccentric device 11, whereby uponrotation of the eccentric device the crosspiece 10 is given areciprocating motion. The crosspiece 10 then subjects the resilient wallof the pump chambers 1 and 2 to periodic inward pressures. Theelasticity of the wall is chosen so as to make it adapt itself to thecrosspiece during the return movement of the latter subsequent to thepressure period. If no counterpressure member is arranged so as to limitthe movements of the opposite wall, it will take part in theoscillations of the resilient wall. The pump chamber volume willtherefore remain constant over the whole period of the oscillations ofthe crosspiece and the pump output will thus be at a minimum. On theother hand, if a fixed counterpressure member is arranged for theopposite wall, the greatest possible variation in the vol ume of thepump chamber will be obtained during the oscillations of the crosspiece10, so that in this case a maximum of pump output will be obtained.

A counterpressure member is arranged to provide a control of theeffective pump volume discharged for each stroke, the effectiveness ofthis member being controllable in dependence upon the desired pumpoutput. The counterpressure member is in the form of a pressure chamberhaving a resilient wall facing the pump chamber. The pressure chambercontains a pressure medium, the pressure of which depends on the desiredpump output. In the embodiment of the invention shown in Figure 1, thepressure chamber comprises a rubber tube 12, 13, which is disposedbetween the pump chamber 1, 2 and a fixed support 14, 15. Each of thechambers 12 and 13 is connected via conduits 16 to 18 to a valve device19, which in its turn is provided with an inlet conduit 20 for thepressure medium and an outlet conduit 21 for the same. The pressuremedium may, for instance, consist of a gas, preferably oxygen underincreased pressure, and the gas can then also be used for theoxygenation of the blood pumped through the arrangement.

The valve device comprises a needle valve 23-, which is inserted betweenthe conduits 20 and 18. The needle valve is of such construction thatits needle is free to move in its boring even after the valve hasclosed. The purpose of this arrangement will be apparent from thefollowing. A second needle valve belonging to the valve device isinserted between the conduits 18 and 21 and can be adjusted manually bymeans of a knob 25 to a position permitting a suitable amount of gas toflow out through the conduit 21. Finally, the valve device comprises avalve 26, which, when opened, allows gas in the pressure chambers 12 and13 and in the conduits 1618 to flow directly out into the surroundingair.

The valve 23 in the connection between the conduits 20 and 18 isprovided with a spring 27 urging the valve towards its open position.The spring operates on a flange 28 on the needle and this flange alsoserves to limit the opening movement of the valve. The other end of theneedle is shaped as a control button 29, which is adapted to be actuatedby one end of a lever 31 of first order fulcrumed at a point 30. Thisend of the lever is additionally acted on by a spring 32. The other endof the lever is connected by means of a rod 33 with a member which isresponsive to the level of the liquid in a container 34. This membercomprises, in the embodiment of Figure 1, a movable membrane 35 arrangedat the bottom of the container 34, the membrane being, in accordancewith the above, connected with the lever 33 such as by means of a disc36 attached thereto. Upon a decrease in the volume of the liquid, whichcorresponds to a lowered level in the container 34, the membrane 35 israised under the influence of the spring 32, whereby the needle valve 23is actuated towards its closed position. The needle valve is againopened when the amount of liquid in the container 34 increases.

The valve 26 is arranged to prevent the amount of liquid in thecontainer 34 to decrease below a predetermined value. To this end, thevalve 26 is responsive to the right-hand part of the lever 3-1 so as toopen when the membrane 35 is raised a predetermined amount into thecontainer 34 by the spring 32. This occurs when the valve 23 has beenclosed completely, but it is still possible at this stage for its needleto be brought further down into the boring. The pressure medium in thecontainers 12 and 13 and in the conduits 1618 is then free to flow outin the surrounding air. The valve 26, as is apparent from the figure, isprovided with a pair of pistons, between which the pressure mediumflows, which provides a balanced action for the valve in such a way thatthe pressure medium does not impart a tendency to the valve to bedisplaced in either direction, thus obviating a back action on themembrane 35.

In the explanation of the operation of the arrangement, it may beassumed to begin with that the inlet conduit leading to the container 34as well as the inlet 7 to the pump chambers 1 and 2 and the chambersthemselves and also the outlet conduit 8 are completely filled withblood, and also that the amount of the blood in the container 34 reachesa predetermined level. This level may be assumed to be chosen such thatthe needle valve 23 is held in an intermediate position, at which thepressure medium flows in from the conduit 28 through the conduits 18, 16and 17 to the pressure chambers 12 and 13. Furthermore, it is assumedthat the needle valve 24 allows a portion of the pressure medium to flowout through the conduit 21. Thus, the pressure in the conduits 16--18 isheld constant and the pressure chambers 12 and 13 are inflated to anintermediate position. When the eccentric 11 is made to rotate, therebymaking the crosspiece perform an oscillating motion, a certain amount ofbloodis pumped along through the pump chambers 1 and 2. The chambersoperate alternately, so that a comparatively even flow of blood isobtained through the conduits 7 and 8. With the pump operating in thisfashion, the level of the liquid in the container 34 goes down andcauses the membrane 35 to rise. The membrane then actuates the needlevalve 23 via the rod 33 and the lever 31, which causes a decreasedamount of pressure medium to be supplied to the conduit system 1618.This decreases the inflation of the pressure chambers 12 and 13 andmakes the walls thereof more resilient. This in turn diminishes theoutput of the pump and counteracts, on the assumption of a constantinflow, the lowering of the liquid level in the container 34. Thearrangement is therefore self-adjusting to a constant level of theliquid in the container 34. This level can be preadjusted manually byvarying the tension of the spring 32, the level in the container 34being made to rise upon an increase in the spring tension.

In the embodiment of the invention shown, the pump chambers 1 and 2 aswell as the pressure chambers 12 and 13 were constructed in the form oftubes or sleeves, but the same effect can be obtained also if one ofthese members contains a fixed or rigid wall.

Figure 2 shows another embodiment of the present invention, wherein thepressure chambers 12 and 13 are arranged between the crosspiece 10 andthe pump chambers 1 and 2. Furthermore, the level-responsive member incontainer 34, instead of being in a form of a membrane, consists of afloat 37 which controls the valve device 19 by means of levers 3 1 and38 and rods 39 and 40.

What is claimed is:

1. Control arrangement in a pump having a fixed member and areciprocating member comprising a pump chamber having an inlet and anoutlet, said pump chamber having walls of a resilient material and beingdisposed between the reciprocating member and the fixed member, aflexible pressure chamber disposed between the reciprocating member andthe fixed member and abutting said pump chamber, a source of fluidmedium connected to said pressure chamber, a container connected to theinlet of said pump chamber, and means connected to said source of fluidmedium and responsive to the liquid level within said container forcontrolling the supply of fluid to said pressure chamber.

2. Control arrangement according to claim 1 wherein said pressurechamber is disposed between the reciprocating member and said pumpchamber.

3. Control arrangement according to claim 1 wherein said pressurechamber is disposed between the fixed member and said pump chamber.

4. Control arrangement according to claim 1, wherein the said liquidresponsive means includes a membrane disposed in the bottom surface ofsaid container.

5. Control arrangement according to claim 1, wherein said liquidresponsive means includes a float disposed in said container.

6. Control arrangement according to claim 1, wherein said liquidresponsive means includes a normally closed valve which is adapted to beopened when a predetermined level is present in the container.

References Cited in the file of this patent UNITED STATES PATENTS

